A present trend in the market of customer telephone station equipment is to provide a miniature or so-called modular jack at a wall outlet and in a base of a telephone set with a modular plug on each end of a line cord by which the base can be connected to the wall outlet. It is not uncommon to provide a wall jack in any number of rooms of a premises, for example, to allow a customer to connect and to disconnect telephone sets in accordance with service needs.
This trend has generated a demand for still greater mobility. For example, a customer may wish to place a telephone set at a particular location, but a wall outlet may not be near enough to permit connection with the initially provided line cord. Customers should welcome the opportunity to be able to easily relocate their telephone sets with customized lengths of line cords to extend from the sets to wall outlets. This capability would be similar to customer ability to place lamps or other electrical power consuming devices at desired locations in rooms and to connect them to remotely located outlets through extension cords.
A coupler for allowing the facile interconnection of modular plug-terminated telephone cords is disclosed and claimed in a pending commonly assigned application Ser. No. 06/081,604 which was filed on Oct. 3, 1979, in the name of E. C. Hardesty and which issued on May 19, 1981 as U.S. Pat. No. 4,268,109. That coupler includes two portions made of a dielectric material which when assembled to form a housing cooperate to hold a plurality of wire-like contact elements spaced apart to engage terminals of a modular plug that is inserted into each end of the coupler. While this device facilitates customer extension of telephone service, it does require the assembly of two plastic portions which increases the cost of manufacture.
While customer combinations of cords satisfies the desire for convenience and portability, it can lead to one problem which must be overcome. As is well known, most telephone cords are made by helically wrapping a plurality of tinsel ribbons about a center core and then insulating the ribbons. If the loop length from the wall terminal to the telephone and return is too lengthy, transmission characteristics will be affected because of excessive resistance. It has been recommended that the customer be allowed to use one twenty-five foot length of cordage comprising stranded conductors, which has a lower resistance the tinsel conductor cordage, in addition to the standard length line cord which is generally supplied with the telephone set. This restriction could be circumvented by the customer if couplers such as those in the above-identified Hardesty application were used.
Seemingly, the prior art is devoid of any device which may be used to satisfy these demands. What is needed is a device which provides the customer with flexibility in telephone set repositioning while preventing inadvertent connection of unacceptably high resistance cords by having a lock-in feature for securing one terminated end of a low resistance cord from facile withdrawal by a customer. The sought-after device is one having a unipartite housing which is relatively simple and inexpensive to manufacture and one which facilitates automatic manufacture.